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For more from Nicole Kidman, watch the full episode of The Jess Cagle Interview, available now on the new People/Entertainment Weekly Network (PEN). Go to PEOPLE.com/PEN, or download the PEN app on Apple TV, Roku Players, Amazon Fire TV, Xumo, Chromecast, iOS and Android devices.

In her new movie Lion, Nicole Kidman plays Sue Brierley, an Australian woman who adopted a young boy named Saroo after he was separated from his family in India.

It’s a touching true story based on Saroo Brierley’s autobiography A Long Way Home — and a role that hits close to home for Kidman, who is an adoptive mother herself to children Isabella, 23, and Connor, 21, with ex-husband Tom Cruise. (She is also mom to Sunday Rose, 8, and Faith Margaret, 5, with husband Keith Urban).

On the latest episode of The Jess Cagle Interview, Kidman opens up to PEOPLE and Entertainment Weekly’s editorial director about how she connected with the material — and the story that she “couldn’t believe” was true at first.

Kidman had the chance to meet the real-life Sue to prepare for the role. She recalls how, in a frank chat at the actress’ apartment in Sydney, the two “basically bared [themselves] to each other” and “formed an immediate spiritual bond.”

Asked if, as an adoptive mother, one prepares for the moment when one’s child wonders about meeting his or her biological parents, Kidman said both she and Sue had.

“It’s very much a part of the whole relationship, so it needs to be addressed [and] discussed,” she said. “I don’t know about other people’s lives, [but] as parents of adopted children, the advice [we were given] was, ‘If they want to find their birth parents, you support that.’ “